Technological advances in microelectronics and digital computing systems have resulted in the proliferation of digital computer networks, enabling the distribution of networking services across a wide range of computers participating in the network and over various communications media. Advances in distributing applications have also resulted in a client-server architecture for applications. Under the architecture, the portions of the application that interact with the user are typically separated from the portions of the application that fulfill client processing requests. Typically, the portions of an application that interact with the user are called a client applications or client software, whereas the portions of the application that service requests made by the client applications are called a server applications or server software. In a network environment, the client applications and server applications are generally executed on different computers.
Historically, digital networks in the form of local area networks, a physical collection of personal computers interconnected with network cabling and network interface cards, consisted of a single network server and multiple network clients. To manage which network clients could access the network server, as well as what files, printers, printer queues, and server applications were available to the network clients, the network server maintained information on each of the resources that were attached to the server and the identities of the network clients and users who could use the services of the network server and the scope and nature of the services available to the network clients and users.
As local area networks became more popular, networks grew in size requiring several servers to service the needs of users. With increased size and complexity of networks, came the need for easier management of network servers. Users required access to an increasing number of services that were located on an increasing number of network servers. Several vendors began offering networking servers. Each vendor implemented a different scheme of providing networking services information. In addition, each network server, because of the way the server maintained information about only its networking services still required management of its resources independently of other network servers.
This insular method of maintaining information of networking services fueled research and development of distributed networking directories, databases that spanned networking servers. Thus far, research has resulted in several potential solutions. Three technologies currently hold greater promise for replacing the large number of insular, idiosyncratic directories that now litter many an enterprise's numerous local-area networks and electronic-mail systems. One approach exploits the X.500 distributed network information directory services protocol developed as published by the CCIT and Open Systems Interconnect consortium.
However, while the X.500 protocol appears to hold the greatest promise to provide a robust, distributed directory, the X.500 protocol has been slow to gain acceptance. The X.500 protocol has been plagued from the start with management, interoperability and security problems. The X.500 protocol specification describes a technical framework, interoperability requirements and compliance criteria but does not describe specific implementations. Thus many of the details of implementation have been left up to systems providers.
The X.500 protocol specification describes a distributed directory. The directory provides information services to network clients. The information in the directory can be read as well as modified by users who have applicable access rights.
The information stored in the directory is a collection of objects with associated attributes or properties. FIG. 1 shows an object called "Computer" with some associated properties, such as owner, operator, status, etc. The values of the properties are not shown in the figure but an example of a value for "Owner" might be "Fred." Objects in the directory and their names correspond to things that humans relate to when dealing with computers, namely, users, printers, print queues, networks and information. Objects such as countries, organizations, networks, people and computers are objects you might find in the directory as well.
The directory provides information to users by giving users a hierarchical view of all of the information contained in the directory. The hierarchical view is generally in the form of a tree. FIG. 2 shows a directory. Each of the branches and terminating points or leaves represent objects in the directory. Generally, implementations of the directory organize objects in subtrees, partitions or domains. FIG. 2 also shows the directory organized into partitions or domains. Multiple copies of each partition may be stored in the directory. Software schemas define and determine the number and types of replicas of each partition.
Multiple replicas of a partition are needed to reduce network storage and traffic requirements and speed up directory searches. Replicas are stored in name servers. A name server is a computer in the network, usually a network server. More than one partition can be stored in a name server. Partitions stored in a name server need not be contiguous.
The directory tree provides a logical means of searching for information. The tree is generally patterned after logical groupings such as organizations, organizational units, computers and users. These logical groupings, while extremely useful in helping users find relevant information also creates significant problems in managing the directory.
Each partition forms a major subtree of the directory. Taken together, the partitions form a hierarchical tree of partitions that leads back to a root partition containing the root directory. Where boundaries of two partitions meet, the partition closer to the root is considered superior, and the partition farther from the root is considered subordinate. Thus, FIG. 2, partitions E and C are subordinate to the other partitions.
The present invention solves one of those problems. As objects of the directory change, the directory must be changed as well. Organizations, organizational units, computers and users all move. Today, the legal department may be reporting through the finance department. Tomorrow, one of the employees of the finance department might be moved to marketing. Prior to the invention, systems administrators responsible for maintaining a directory had to move each object in the directory in response to a real change in the status of the object. Unfortunately, no facilities existed for moving course grain objects such as an entire department. If the legal department was to be moved to report to the finance department, each object in the legal subtree had to be moved separately.